I'm sure you'll get a lot of great responses but wanted to chime in because we have recently been going through similar with our 17mth old. It could be good ole fashion teething. My 17mth old would be cranky when he was teething the front teeth but nothing major. When we started on back teeth he started waking up between 3 and 5ish with uncontrollable crying. After trying a few different things (bottle, rocking, etc) and him still fighting laying back down we would eventually take him to our bed where sometimes he would fall back to sleep. When he wouldn't we figured teething and would give a little tylenol and orajel. This seemed to do the trick. Sometimes he would want to stay in our bed right next to me and other times he wanted to go back to his bed.
If not teething you might want to put him to bed later. We have even done that (moved bed time to 8:30 and wake up at 6:30 to 6:45) and changed from 2 short naps to 1 long nap right after lunch. Plus, keeping to a routine definitely helps. We go in the same order as often as possible, (dinner, a little play time, bath, book, prayer, bed). Good Luck